earth science – chap. 2 – sect.1
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Earth Science – Chap. 2 – Sect.1. Objectives 1. List the characteristics of earth’s three compositional zones and 5 structural zones 2. Explain how studies of seismic waves have provided information about earth’s interior - PowerPoint PPT PresentationTRANSCRIPT
EARTH SCIENCE – CHAP. 2 – SECT.1
•OBJECTIVES•1 . L I ST T H E C HAR ACT ER IS T I C S O F EART H’ S T H R EE C O M PO S I T IO N AL ZO NES AND 5 ST R UC T UR AL ZO NES•2 . EX PL A I N H O W ST UDI ES O F SE I SM I C WAVES HAVE P R OV I DED I NFO R MAT I O N AB OU T EART H’S I NT ER I O R•3 . DEF I N E M AGN ET O SPH ER E AND I DENT I FY T HE PO SS I B L E S OU R C E O F EART H’S MAG N ET I SM•4 . SU MMAR I Z E NEWT O N’S L AW O F G R AV I TAT I O N
STATE SCIENCE STANDARDS
Recognize that the force of gravity keeps planets in orbit around the sun and influences objects on Earth and other planets (i.e., tides, ability of humans to move and function). Differentiate between an object’s mass and weight.
Investigate how thermal convection relates to movement of materials. Apply this knowledge in explaining the cause of movement of the Earth’s plates.
Describe energy sources, processes, and transformations of Earth materials as they progress through the rock cycle to form new sedimentary, metamorphic, and igneous rocks. Discuss how the cycling of rock is continuous.
EARTH STATS• Earth is not a perfect sphere• Earth is an oblate spheroid• Circumference around poles = 40,007 km• Circumference around the equator = 40,074 km• The spinning of the earth causes centrifugal
force, causing the poles to flatten and the equator to bulge
• Distance between highest mountain and lowest part of ocean = ~ 20 km.
• Average diameter of earth = 12,735 km.
OBLATE SPHEROID
HYDROSPHERE Earth cover by 71% water97% of that water is salt water3 % fresh water is in lakes, river,
streams, groundwater and frozen in glaciers and icecaps.
1% available for use by living organisms
All of earth’s water is know as the hydrosphere
HYROSPHERE
ATMOSPHEREThe gases in the earth’s
atmosphere supply oxygen to living organisms and shield the earth from harmful solar radiation
78% - nitrogen21% - oxygenLast 1% includes: CO2 , argon and
helium
CARBON DIOXIDE IN THE ATMOSPHERE
What does 400 ppm mean?.04% of atmosphere400 parts of Carbon Dioxide per 1
Million parts of atmosphereWhy is carbon dioxide so
important in today’s society?
LIVING ORGANISMS AND NITROGEN
Nitrogen is an essential component for life on Earth and makes up 78% of the atmosphere.
If humans need nitrogen to survive do we get t from the atmosphere like we get Oxygen?
If not, where do we get it?
NITROGERN-FIXING BACTERIA
PLANTS WITH NITROGEN_FIXING BACTERIA
LET’S EXPLORE NITROGEN_FIXING BACTERIA
With your partner gather some samples of clover from the A.I. Nature Area
Be careful to gently pull the plant from the ground preserving the root system
Locate the nitrogen-fixing bacteria nodules attached to the roots
Carefully place them onto a slide and observe them under a microscope
Make some observations in your notebooks!
EARTH’S INTERIORScientists use seismic waves to
speculate on the composition of earth’s interior
Seismic waves are vibrations that travel through the earth
Seismic wave studies have helped scientist determine that the earth is made up of three (3) major zones – compositional
(5) structural zones
EARTH’S LAYERS
COMPOSITIONAL ZONES OF THE EARTH
Crust: thin, outermost zone of earthMakes up 1% of earth’s massOceanic crust found beneath oceansBetween 5 and 10 km. ThickDenseComposed of mostly iron and magnesium
Continental crust makes up continentsBetween 15 and 80 km. Thick (thickest beneath mountain ranges)
Less denseComposed mostly of silicon and oxygen
COMPOSITIONAL ZONES CONTINUED
Mantle: zone below crustNearly 2,900 km thick (1,798
miles)Makes up almost 2/3’s of
earth’s mass
Core: below mantle and forms center of earth, made mostly of iron, makes up approx. 1/3 of earth’s mass
5 - STRUCTURAL ZONESLithosphere: the uppermost part of mantle and the crust. A rigid layer 15 – 300 km. ThickAsthenosphere: just below the lithosphere, approx. 200 km. Thick, plastic like (solid rock with ability to flow due to enormous temp. and pressure)Mesosphere: Below the Asthenosphere – solid rock-Approx. 2900 km
Outer core: dense, liquid layer about 2,250 km. Thick (1395 miles)Inner core: dense, solid sphere with a radius of 1,228 km. (761 miles)
SEISMIC WAVESPrimary waves (p-waves): travel through
solids, liquids and gases. Travel faster than s-waves
Secondary waves (s-waves): only travel through solids, slower than p-waves
Speed and direction of p and s waves affected by composition of material they travel through
Both waves travel faster through more rigid materials
THE MOHOIn 1909 Andrija Mohorovicic, a Croatian
scientist, discovered that the speed of seismic waves increases abruptly 32 to 70 km below earth’s surface. This change in speed marks the boundary between the crust and the mantle and is known as The Mohorovicic Discontinuity or simply The Moho.
The increase in speed indicates that the mantle must be denser than the crust.
ANDRIJA MOHOROVICIC- -THE MAN!
OTHER CHANGES IN WAVE VELOCITY
Approx. 100 km below the Moho the waves decrease in velocity at the boundary between the lithosphere and the less dense asthenosphere
Seismic waves increase in speed after this boundary until approx. 2,900 km.
At 2,900 km, p-waves slow down and s-waves disappear entirely. This marks the boundary between the mantle and the outer core (liquid)
At a depth of approx. 5,150 km (3,193 miles) the p-waves speed up again marking the boundary between the outer core and the inner core (dense solid)
SHADOW ZONESLocations on earth’s surface where neither
s-waves nor p-waves are detected (or where only p-waves are detected)
Caused by earth’s non-uniform composition of materials which causes the waves to bend and change direction due to speed differences of the waves
S-waves cannot travel through the liquid outer core and p-waves bend with different density materials forming shadow zones
SHADOW ZONE
EARTH AS A MAGNETEarth has two magnetic poles:The Northern Geomagnetic Pole and the Southern
Geomagnetic Pole with lines of force between the twoMagnetosphere: the area of space that extends beyond
the atmosphere that is affected by the magnetic fieldMagnetic field thought to be generated by the flow of
liquid iron in the outer core due to the conductivity of the iron producing electrical currents
Problem: the moon and sun both have a magnetic field but the sun has very little iron and the moon has no liquid core. This indicated that there may be some other force producing the magnetic fields.
EARTH’S GRAVITYGravity: the force of attraction that exists
between all matter in the universe, discovered by Sir Isaac Newton and described in his law of gravitation
Law of Gravitation: states that the force of two objects depends on their masses and the distance between them. The larger the masses of the two objects and the closer together they are, the greater will be the force between them.
EARTH’S GRAVITYThe mass of the earth exerts a force of
gravity that pulls objects toward the center of the earth.
Weight: the measure of the strength of the pull of gravity on an object. (measured in Newtons- on earth’s surface 1 kilogram of mass weighs about 10 N)
How much would a mass of 2-kg weigh?How much would a mass of 10-kg weigh?
WEIGHT AND MASSMass: the amount of matter in an objectWeight: the force of gravity on an objectMass of an object does not change with
location, weight doesThe weight of an object depends on its
mass and the distance from the earth’s center
An object would weigh approx. 0.3 % less at the equator than at the North Pole due to the difference in distance from the center of the earth.
QUIZ – CHAPTER 2, SECT 1
QUIZ
HOMEWORK
Read Chapter 2, sections 2 & 3Do section reviews 2.2 & 2.3- 1 – 12, 1 - 10
EXIT TICKET1.Would a person weigh more at the North
Pole or the Equator? Why?2.What is meant by 400 ppm? Why is it
significant in today’s society?3.Describe the Moho.4.Describe the difference between a “P”
wave and an “S” wave.